What advice would you give to someone looking to buy a C4?
90 or newer.
First choice - '90 to '95 ZR-1 - they are GREAT cars. The '90-'92 MYs were rated at 375hp and the '93-'95 MYs were rated at 405hp. But just over 400 were built during each of the last three years they are a little more spendy. Don't be afraid of the LT5 engine as there are plenty of them out there with odometer readings up into 6 figures and still running strong.
Second choice - '95 or '96 (the '92-'94 LT1 had issues with the OPT-Spark). A '96 with the LT4/6 speed manual is a SWEET ride!
Jim Olson